Measurement of Singly Cabibbo-Suppressed Decays $D^{0}\toπ^{0}π^{0}π^{0}$, $π^{0}π^{0}η$, $π^{0}ηη$ and $ηηη$
Using a data sample of $e^+e^-$ collision data corresponding to an integrated luminosity of 2.93 $fb^{-1}$ collected with the BESIII detector at a center-of-mass energy of $\sqrt{s}= 3.773~GeV$,we search for the singly Cabibbo-suppressed decays $D^{0}\toπ^{0}π^{0}π^{0}$, $π^{0}π^{0}η$, $π^{0}ηη$ and $ηηη$ using the double tag method. The absolute branching fractions are measured to be $\mathcal{B}(D^{0}\toπ^{0}π^{0}π^{0}) = (2.0 \pm 0.4 \pm 0.3)\times 10^{-4}$, $\mathcal{B}(D^{0}\toπ^{0}π^{0}η) = (3.8 \pm 1.1 \pm 0.7)\times 10^{-4}$ and $\mathcal{B}(D^{0}\toπ^{0}ηη) = (7.3 \pm 1.6 \pm 1.5)\times 10^{-4}$ with the statistical significances of $4.8σ$, $3.8σ$ and $5.5σ$, respectively, where the first uncertainties are statistical and the second ones systematic. No significant signal of $D^{0}\toηηη$ is found, and the upper limit on its decay branching fraction is set to be $\mathcal{B}(D^{0}\toηηη) < 1.3 \times 10^{-4}$ at the $90\%$ confidence level.